/*
 * Licensed to ObjectStyle LLC under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ObjectStyle LLC licenses
 * this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package io.bootique;

import java.util.Collection;
import java.util.Objects;
import java.util.function.Supplier;

class DeferredModulesSource implements Supplier<Collection<BQModule>> {

    private Collection<BQModule> modules;

    @Override
    public Collection<BQModule> get() {

        if (modules == null) {
            throw new IllegalStateException("DeferredModuleMetadataSupplier is not initialized");
        }

        return modules;
    }

    // this method must be called exactly once before 'get' can be invoked....
    void init(Collection<BQModule> modules) {

        if (this.modules != null) {
            throw new IllegalStateException("DeferredModuleMetadataSupplier is already initialized");
        }

        this.modules = Objects.requireNonNull(modules);
    }
}
